Luke 17:5

And the apostles said unto the Lord, Increase our faith. And the Lord said, If ye had faith as a grain of mustard seed, ye would say unto this sycamine tree, Be thou rooted up, and be thou planted in the sea; and it would obey you.

This is the third of the four pronouncements. The apostle's reaction to the command of Jesus for what amounts to unlimited forgiveness appeared to them such a monstrous task that they supposed they needed a special measure of faith to be able to comply with it. The teaching here is that the faith they had was more than enough to enable it, provided only that they got on with the DOING of it.

Apostles ... Lord ... Those commentators who suppose that these terms were retrospectively incorporated in Luke's Gospel at a time long after the events, and at a time when the early church had "developed" these words are wrong. Jesus himself named the Twelve "apostles" (Luke 6:13); and they referred to Jesus as "Lord," using the word as a reference to the Godhead. Drowning Peter cried out, saying, "Lord, save me," and this student of the word of God will never consent to view these words as the equivalent of "Rabbi, save me" (Matthew 14:30).

Sycamine tree ... "This word sometimes means the mulberry tree, sometimes the sycamore."[7]

What did Jesus means by this promise? There are two things in it: (a)the forgiveness of those who sin against us is, humanly speaking, an impossibility, comparable to the outlandish wonder in view here; and (b) the faith of Christians, without any providential increase of it, is more than enough to enable it to be done.

Miller was right in affirming that such a wonder as Jesus promised here suggests "that genuine faith can accomplish what experience, reason, and probability would deny, if it is exercised within God's will."[8] Hobbs was sure that no miraculous ability was promised Christians in this; because, said he, "We cannot even transplant violets in a garden, to say nothing of transplanting trees from the land into the sea."[9] Jesus' true meaning is found in the Jewish usage of such extravagant figures of speech. "Rabbis of intellectual eminence were often called `uprooters of mountains' in allusion to their powers of solving difficult questions";[10] and, significantly, Matthew quoted Jesus using the term "mountain" in this same context on another occasion (Matthew 17:20). This, of course, is the same figure and should be understood spiritually.

[7] J. R. Dummelow, Commentary on the Holy Bible (New York: The Macmillan Company, 1937), p. 762.

[8] Donald G. Miller, The Layman's Commentary (Richmond: John Knox Press, 1959), p. 125.

[9] Herschel H. Hobbs, op. cit., p. 247.

[10] John William Russell, Compact Commentary on the New Testament (Grand Rapids, Michigan: Baker Book House, 1964), p. 182.